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fix for locking in Windows (CVS 760)

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FossilOrigin-Name: 83add34f64895a4b465881213eba82f3b1f5c964
This commit is contained in:
mike
2002-10-17 00:38:54 +00:00
parent f1f0fa0769
commit 710dcfbde5
3 changed files with 84 additions and 35 deletions
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103
src/os.c
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@@ -492,7 +492,7 @@ int sqliteOsRead(OsFile *id, void *pBuf, int amt){
if( !ReadFile(id->h, pBuf, amt, &got, 0) ){
got = 0;
}
if( got==amt ){
if( (int)got==amt ){
return SQLITE_OK;
}else{
return SQLITE_IOERR;
@@ -627,10 +627,64 @@ int sqliteOsFileSize(OsFile *id, int *pSize){
** lock and get the read lock without another process jumping into the
** middle and messing us up. The same argument applies to sqliteOsWriteLock().
**
** Locks must be obtained in an area that does not overlap the "real data area"
** otherwise read/write operations will conflict with lock operations. Locking beyond EOF
** is allowed in windows.
**
** There are a finite number of read locks under windows. That number
** is determined by the following variable:
*/
#define MX_LOCKBYTE 10240
#define MX_LOCKBYTE 0xFFF0
#if OS_WIN
// get the platform id to decide how to calculate the lock offset
int mkPlatformId(void){
static long init=0;
static int pid=VER_PLATFORM_WIN32_WINDOWS;
OSVERSIONINFOA info;
if (!init) {
if (InterlockedIncrement(&init)==1)
{
info.dwOSVersionInfoSize=sizeof(info);
if (GetVersionEx(&info)) pid=info.dwPlatformId;
}
}
return pid;
}
// locks and unlocks beyond eof. uses platformid to move the lock as far as possible.
int mklock(HANDLE h, WORD base, WORD size)
{
if (mkPlatformId()==VER_PLATFORM_WIN32_WINDOWS)
return LockFile(h,0xFFFF0000+base,0,size,0);
else
return LockFile(h,base,0xFFFFFFFF,size,0);
}
int mkunlock(HANDLE h, WORD base, WORD size)
{
if (mkPlatformId()==VER_PLATFORM_WIN32_WINDOWS)
return UnlockFile(h,0xFFFF0000+base,0,size,0);
else
return UnlockFile(h,base,0xFFFFFFFF,size,0);
}
//obtain the sync lock on a handle
void synclock(HANDLE h){
while (!mklock(h,0,1)) Sleep(1);
}
void syncunlock(HANDLE h){
mkunlock(h,0,1);
}
#endif
/*
** Change the status of the lock on the file "id" to be a readlock.
@@ -639,6 +693,7 @@ int sqliteOsFileSize(OsFile *id, int *pSize){
**
** Return SQLITE_OK on success and SQLITE_BUSY on failure.
*/
int sqliteOsReadLock(OsFile *id){
#if OS_UNIX
int rc;
@@ -674,11 +729,12 @@ int sqliteOsReadLock(OsFile *id){
}else{
int lk = (sqliteRandomInteger() & 0x7ffffff)%MX_LOCKBYTE + 1;
int res;
if( (res = LockFile(id->h, 0, 0, 1, 0))!=0 ){
UnlockFile(id->h, 1, 0, MX_LOCKBYTE, 0);
res = LockFile(id->h, lk, 0, 1, 0);
UnlockFile(id->h, 0, 0, 1, 0);
}
synclock(id->h);
if (id->locked<0) mkunlock(id->h,1,MX_LOCKBYTE); // release write lock if we have it
res=mklock(id->h,lk,1);
syncunlock(id->h);
if( res ){
id->locked = lk;
rc = SQLITE_OK;
@@ -722,15 +778,13 @@ int sqliteOsWriteLock(OsFile *id){
rc = SQLITE_OK;
}else{
int res;
if( (res = LockFile(id->h, 0, 0, 1, 0))!=0 ){
if( id->locked==0 || UnlockFile(id->h, id->locked, 0, 1, 0) ){
res = LockFile(id->h, 1, 0, MX_LOCKBYTE, 0);
}else{
res = 0;
}
UnlockFile(id->h, 0, 0, 1, 0);
}
if( res ){
synclock(id->h);
if (id->locked>0) mkunlock(id->h,id->locked,1); // release read lock
res=mklock(id->h,1,MX_LOCKBYTE);
syncunlock(id->h);
if(res){
id->locked = -1;
rc = SQLITE_OK;
}else{
@@ -772,18 +826,13 @@ int sqliteOsUnlock(OsFile *id){
#endif
#if OS_WIN
int rc;
if( id->locked==0 ){
rc = SQLITE_OK;
}else if( id->locked<0 ){
UnlockFile(id->h, 1, 0, MX_LOCKBYTE, 0);
rc = SQLITE_OK;
id->locked = 0;
}else{
UnlockFile(id->h, id->locked, 0, 1, 0);
rc = SQLITE_OK;
id->locked = 0;
if(id->locked<0 ) {
mkunlock(id->h,1,MX_LOCKBYTE);
}else if (id->locked>0) {
mkunlock(id->h,id->locked,1);
}
return rc;
id->locked = 0;
return SQLITE_OK;
#endif
}